Effect of seawater, aluminate cement and alumina-rich spinel on pelletised CaO-based sorbents for calcium looping

Calcium looping (CaL) is considered as an emerging technology to reduce CO2 emissions in power generation systems and carbon-intensive industries. The main disadvantage of this technology is reactivity decay over carbonation/calcination cycles due to sintering. The main objective of this study was to evaluate the performance of novel sorbents for CaL. Three types of pelletized CaO-based sorbents for CO2 capture were developed by adding aluminate cement, aluminate cement with seawater, or alumina-rich spinel to calcined limestone. Different concentrations of seawater in deionized water solutions were tested: 1, 10, 25, and 50 vol %. All samples were tested in a thermogravimetric analyzer (TGA) under two different calcination conditions: mild (N2 atmosphere and 850 °C during calcination) and realistic (CO2 atmosphere and 950 °C during calcination). The samples were characterized using SEM and EDX. Aluminate cement CaO-based sorbents exhibited better performance in the TGA tests (25% conversion after 20 cycles achieved by limestone and 35% with aluminate cement CaO-based pellets, under mild conditions, and 11% conversion after 20 cycles with limestone compared to 15% utilizing aluminate cement CaO-based pellets, under realistic conditions). However, doping had a negative effect on the reactivity of the sorbent. Moreover, alumina rich spinel CaO-based sorbents showed the worst performance

Hybrid microwave processing of particulate materials using a novel non-conventional fluidised bed

Microwave technologies have been widely used in various industries for heating applications, offering several benefits when compared to other conventional systems including faster heating rates, selective and volumetric heating, instantaneous control over energy delivery and the potential to be powered by a sustainable energy source. However, challenges arise when it comes to higher temperature industrial processing (exceeding ~100 ºC). Achieving heating homogeneity and uniform material treatment remains a notable issue and the requirement for bespoke designs often leads to expensive equipment and materials of construction. Most of the existing techniques to overcome those challenges rely on the complexity of the use of moving parts. Microwave fluidised-bed reactors have been subject to extensive research for their use in industrial applications, primarily due to their advantageous particle mixing capabilities, accompanied by the rapid and efficient heating provided by microwave energy. Nonetheless, these systems still have limitations, including reactor tube fragility, potential overheating, and limited overall robustness. A novel hybrid microwave toroidal fluidised-bed system, TorWave reactor, was developed collaboratively by the University of Nottingham and Torftech Ltd. to address the mentioned challenges when it comes to scaling up microwave processors. In this work, a proof of concept one-litre hybrid microwave toroidal fluidised-bed reactor, TorWave 400 (T400) prototype, has been constructed and investigated for its use in microwave processing of particulate materials with particular emphasis in the industrial case study of coffee roasting. Hydrodynamic characterisation of the T400 prototype has been carried out for the definition of its regimes of operation: packed bed, air channelling/bubbling, slugging, toroidal fluidisation and fast fluidisation or elutriation. Moreover, the developed hybrid microwave system has demonstrated the ability to overcome many of the challenges associated with existing microwave technologies including improved heating uniformity, process reproducibility and excellent temperature control. Moreover, this system has proven to achieve an excellent level of treatment homogeneity with a temperature coefficient of variation across the entire surface of the bed of the order of 2 %, showing an improvement over existing microwave technologies, placing it as a viable candidate for scaling-up. A mathematical model has been created as a possible tool for predicting the temperature profile across given particles for a fixed set of conditions in the T400 prototype. The created mathematical model has been proven to have the ability to predict and reproduce a desired temperature profile for a given material allowing the estimation of the necessary combination of air temperature and microwave power necessary to create any desired temperature profile within a given particle of known properties. Hybrid microwave roasting of coffee beans in a TorWave reactor was assessed for the first time during this thesis as a potential alternative to conventional coffee roasters. The main hypothesis under this investigation is the increased microwave bloating effect over the coffee grains translating into a superior expansion of the beans during roasting generating enriched flavour and aroma profiles due to better solids extractability. Furthermore, the reduction of roasting times and the possibility of being entirely powered by a sustainable source opens the scope for process intensification of coffee roasting by the use of the TorWave technology. Hybrid microwave coffee roasting tests performed during this study showed superior bloating and porosity of the beans when compared to conventional roasts. Moreover, aroma and flavour profiles obtained proved an enhanced concentration of desired volatile compounds in the coffee brew and stronger overall coffee intensity, thus supporting the main hypothesis presented and placing microwave coffee roasting as an alternative to existing conventional methods. Future work includes the optimisation of the process conditions for coffee roasting in the TorWave prototype to assess their impact on the final product. Exploratory work has been started for other prospective industrial applications of the TorWave reactor including drying of grains and expansion of snacks. Further research is recommended in those areas as preliminary results showed potential benefits arising from the use of this novel hybrid microwave technology

Hybrid microwave processing of particulate materials using a novel non-conventional fluidised bed

Microwave technologies have been widely used in various industries for heating applications, offering several benefits when compared to other conventional systems including faster heating rates, selective and volumetric heating, instantaneous control over energy delivery and the potential to be powered by a sustainable energy source. However, challenges arise when it comes to higher temperature industrial processing (exceeding ~100 ºC). Achieving heating homogeneity and uniform material treatment remains a notable issue and the requirement for bespoke designs often leads to expensive equipment and materials of construction. Most of the existing techniques to overcome those challenges rely on the complexity of the use of moving parts. Microwave fluidised-bed reactors have been subject to extensive research for their use in industrial applications, primarily due to their advantageous particle mixing capabilities, accompanied by the rapid and efficient heating provided by microwave energy. Nonetheless, these systems still have limitations, including reactor tube fragility, potential overheating, and limited overall robustness. A novel hybrid microwave toroidal fluidised-bed system, TorWave reactor, was developed collaboratively by the University of Nottingham and Torftech Ltd. to address the mentioned challenges when it comes to scaling up microwave processors. In this work, a proof of concept one-litre hybrid microwave toroidal fluidised-bed reactor, TorWave 400 (T400) prototype, has been constructed and investigated for its use in microwave processing of particulate materials with particular emphasis in the industrial case study of coffee roasting. Hydrodynamic characterisation of the T400 prototype has been carried out for the definition of its regimes of operation: packed bed, air channelling/bubbling, slugging, toroidal fluidisation and fast fluidisation or elutriation. Moreover, the developed hybrid microwave system has demonstrated the ability to overcome many of the challenges associated with existing microwave technologies including improved heating uniformity, process reproducibility and excellent temperature control. Moreover, this system has proven to achieve an excellent level of treatment homogeneity with a temperature coefficient of variation across the entire surface of the bed of the order of 2 %, showing an improvement over existing microwave technologies, placing it as a viable candidate for scaling-up. A mathematical model has been created as a possible tool for predicting the temperature profile across given particles for a fixed set of conditions in the T400 prototype. The created mathematical model has been proven to have the ability to predict and reproduce a desired temperature profile for a given material allowing the estimation of the necessary combination of air temperature and microwave power necessary to create any desired temperature profile within a given particle of known properties. Hybrid microwave roasting of coffee beans in a TorWave reactor was assessed for the first time during this thesis as a potential alternative to conventional coffee roasters. The main hypothesis under this investigation is the increased microwave bloating effect over the coffee grains translating into a superior expansion of the beans during roasting generating enriched flavour and aroma profiles due to better solids extractability. Furthermore, the reduction of roasting times and the possibility of being entirely powered by a sustainable source opens the scope for process intensification of coffee roasting by the use of the TorWave technology. Hybrid microwave coffee roasting tests performed during this study showed superior bloating and porosity of the beans when compared to conventional roasts. Moreover, aroma and flavour profiles obtained proved an enhanced concentration of desired volatile compounds in the coffee brew and stronger overall coffee intensity, thus supporting the main hypothesis presented and placing microwave coffee roasting as an alternative to existing conventional methods. Future work includes the optimisation of the process conditions for coffee roasting in the TorWave prototype to assess their impact on the final product. Exploratory work has been started for other prospective industrial applications of the TorWave reactor including drying of grains and expansion of snacks. Further research is recommended in those areas as preliminary results showed potential benefits arising from the use of this novel hybrid microwave technology

Effect of Seawater, Aluminate Cement, and Alumina-Rich Spinel on Pelletized CaO-Based Sorbents for Calcium Looping

Calcium looping (CaL) is considered as an emerging technology to reduce CO2 emissions in power generation systems and carbon-intensive industries. The main disadvantage of this technology is reactivity decay over carbonation/calcination cycles due to sintering. The main objective of this study was to evaluate the performance of novel sorbents for CaL. Three types of pelletized CaO-based sorbents for CO2 capture were developed by adding aluminate cement, aluminate cement with seawater, or alumina-rich spinel to calcined limestone. Different concentrations of seawater in deionized water solutions were tested: 1, 10, 25, and 50 vol %. All samples were tested in a thermogravimetric analyzer (TGA) under two different calcination conditions: mild (N2 atmosphere and 850 °C during calcination) and realistic (CO2 atmosphere and 950 °C during calcination). The samples were characterized using SEM and EDX. Aluminate cement CaO-based sorbents exhibited better performance in the TGA tests (25% conversion after 20 cycles achieved by limestone and 35% with aluminate cement CaO-based pellets, under mild conditions, and 11% conversion after 20 cycles with limestone compared to 15% utilizing aluminate cement CaO-based pellets, under realistic conditions). However, doping had a negative effect on the reactivity of the sorbent. Moreover, alumina rich spinel CaO-based sorbents showed the worst performance

Solving the microwave heating uniformity conundrum for scalable high-temperature processes via a toroidal fluidised-bed reactor

Challenges exist to implementing high-temperature microwave processes with changing dielectric properties that achieve uniform processing. This paper presents a new high-temperature hybrid microwave processing system which overcomes these challenges in a robust, scalable way, integrating a slotted waveguide ring microwave feed into a toroidal fluidised bed reactor and maintaining its fluidisation behaviour. The prototype operates at a frequency of 2450 MHz with a maximum power of 10 kW and within a temperature range of 50-300°C, though it is scalable to industrial levels. Electromagnetic simulations of the system were experimentally validated using a range of agri-crop feedstocks. Hydrodynamic and thermodynamic reactor characterisation was performed, and treatment performance was quantified regarding surface bed temperature variation. Excellent treatment uniformities were found under microwave and hybrid regimes, with a temperature coefficient of variation (CoV) across the bed's surface below 2 %, an order of magnitude better than existing microwave processes, generally regarded as highly uniform with CoV of approximately 20 %. The integration of microwaves and toroidal fluidised beds, without exposed moving parts, potentially unlocks a range of applications previously inaccessible to microwave technology or fluidised bed technologies on their own. Future work involves process development, techno-economic studies, and large-scale pilot trials

Presentation of the final prototype to the "Chem-E-Car" Competition at the 10th World Congress of Chemical Engineering

El proyecto consistió en la presentación del prototipo Chem-E-Car desarrollado en la UCM en la competición mundial que se celebró durante el transcurso del Congreso Mundial de Ingeniería Química (Barcelona, 30 septiembre-2 de octubre de 2017).The project consisted of the presentation of the Chem-E-Car prototype developed at the UCM in the world competition held during the World Congress of Chemical Engineering (Barcelona, September 30-October 2, 2017).Depto. de Ingeniería Química y de MaterialesFac. de Ciencias QuímicasFALSEsubmitte